theory of channels and collaterals

例句：

1. 1. The river is a major transportation channel for the city.
   这条河流是该市的主要交通通道。
2. 2. The new highway has opened up several new channels of trade.
   新的高速公路开辟了几条新的贸易渠道。
3. 3.The scientist used a channel to conduct experiments in the lab.
   科学家使用一个通道在实验室里进行实验。